questions in simple tense

[akshay vyas]

In simple present and past we make question with do / does / did. but we don't use do/does/did if who / what / which is the subject of the sentence.....

(1) This book belongs to somebody.

Who does this book belong to ?

(2) This word means something.

What does this word mean ?

Here, In both word do and does are used with ?

book and word both are used as a subject, only then they are true.
what are the real subjects of these sentences ?

It appears "somebody" and "something" are the subject, aren't they ?
if yes, then why do does are used with them in these sentences ?

[5jj]

(1) This book belongs to somebody.

Who does this book belong to ?

(2) This word means something.

What does this word mean ?
[...]

what are the real subjects of these sentences ?

I have underlined the grammatical subjects in your sentences.

[engee30]

Actually, I'd say that the subjects of the sentences are this book and this word, respectively.

It appears "somebody" and "something" are the
subject, aren't they ?

No, the two pronouns are objects in those sentences, which explains why they can't be put in the position of subject in an interrogative sentence.

[5jj]

Actually, I'd say that the subjects of the sentences are this book and this word, respectively.

Formally, only the noun in these sentences is the grammatical subject.